Devices intended for ascertaining whether or not a railroad switch is open are quite old and have been used in association with most switch mechanisms for many years in railroad yards, hump yards and on mainlines. Such mechanisms depend mostly upon the accuracy and capability of the switch itself to detect failures that will cause the switch point to open. Many devices are very sophisticated and electronically controlled, and such prior art devices frequently are intended to permit ascertaining whether or not the switch is closed from remote points.
However, even in the light of such sophisticated equipment, railroads continue to suffer derailments. It is believed that the cause for many of these derailments can be traced to conventional mechanisms for detecting whether a switch is open or closed. Such prior art mechanisms are usually of a type which detect an obstructed open switch point, but only if the obstruction results in mechanical pressure directed against the switch machine. If there is no obstruction, the detector mechanism may cause an erroneous reading indicating that the switch is open or closed, when in fact the opposite is true.
It is believed that such detector failures can be traced to loose or worn out movable parts and mechanical components, or poor maintenance or loose ballast conditions, or poor maintenance or loose stockrail braces, or worn out or loose throwrod adjusting nuts, or worn out or defective throw rod baskets, or broken throwrods, or worn out or broken lugs connecting the switch sectors and throwrods. In any of these events, the failure can be traced to the fact that the prior art detector is adjusted and set according to calibration of the detector and the switch point, rather than a positive relationship between the stockrail and the switchrail at the point where they are intended to come together or be separated.
In such failures, even if the conventional detector is initially properly calibrated, changes occur which make the calibration inaccurate. If the calibration is changed by some condition which is not regularly detected, sometimes by a misalignment of merely about 0.05 of an inch, such as movement of the tracks relative to one another or movement of the detector or switch components, which may result from vibrations of a locomotive or rolling stock over the track or by a change in weather conditions, a derailment may result.
The present invention is designed to offer reliability and accuracy for detecting opening and closing movements of the switch points. This invention is characterized by a mechanism securely mounted to the stockrail which positively "feels" the switchtrack in a selected position at the location when the point is selectively opened or closed, so that it positively notes the presence or absence of the switchtrack at the point when the point is closed or open, as desired. If the detector shows the switch is open or if the switch is closed at the point, that fact is made known through a signal system. Such a positive indication of the condition of the point substantially insures the safety of trains traveling over the switchtrack, and improves the detection and guarantees the anticipation of any opening and closing movement of the switch point under any circumstances. The improved mechanism embodying the invention provides accurate detection of changes in the point throwrod adjustment which cause the point to open, including failures due to wearing out of movable parts, misalignments, adverse weather conditions, and breakdown of mechanical components which allow the point to open, causing a derailment.